Tires present a difficult recycling problem. The desirability of recycling is matched by the difficulty of achieving the desired reuse. By some estimates, over a million tires a day are discarded in the United States alone. Landfill disposal of tires has never been a particularly desirable option because the lightweight tires tend to rise to the surface through the overburden. Landfill disposal of tires is becoming even less feasible with the spiraling increase in landfill use charges. Further, many communities are mandating that inherently recyclable products such as tires not be allowed in landfills. Open air storage and stockpiling of tires is dangerous and undesirable. A large stack of discarded tires represents a considerable risk to the pubic safety and health. A large tire fire can be difficult to fight and produces intense air polluting smoke. Mosquitoes may breed in water which collects on the inside of the tires and can spread diseases such as malaria, yellow lever, and spinal meningitis.
Because of the low density of unprocessed waste tires, the cost of transportation to a centralized processing facility can be prohibitive. Most solutions to the disposal of tires have centered around creating a mobile machine for cutting or shredding tires so they may more economically be transported and disposed of. Although the uses of used tires are many, they have not yet proven sufficient to solve the disposal problem. The key to finding more uses for tires involves finer and finer shredding or grinding of the tires. Large, one to two inch chunks of tires may be burned in some coal-fired utility boilers. Granulated tires may be made into playground coverings or added to asphalt paving. If the tires are reduced to a fine powder, they may be directly recycled in new rubber products.
Tires, by their very nature, have been designed to resist cutting and abrasion, and thus can be difficult and costly to reduce to a fine powder. Abrasive grinding of tires has not proven feasible, as the resulting heat tends to ignite the tires.
One known apparatus which shreds tires into small pieces is fed tires which have been cut in half diametrically. The tire segments are flattened out and with the treadside up are fed across a non-moving blade which interdigitates with a plurality of rotating blades. Still, such a tire recycling apparatus requires further steps to reduce the tire to the fine powder required for incorporation into new products. Many types of tire recycling apparatus are know which cut tires into pieces from one eighth of an inch across to four inches across. Quarter inch and eighth inch size particles may be recycled into play ground surfaces. However, such pieces are too large for use in rubber end products such as mud flaps and bridge abutments. Larger pieces must first be fed through a granulator to achieve a desired fine particle size.
What is needed is a readily transportable apparatus which directly converts tires to a fine powder suitable for use in new products.